Justin Bieber has been accused of joking about killing black people and joining the Ku Klux Klan in a shocking new video.

The 20-year-old pop star - who only just recently apologised after a video emerged of him using a racial slur at the age of 15 - is at the center of another controversy as new footage has emerged which allegedly shows him altering the lyrics of his 2009 song "One Less Lonely Girl" by singing, "One less lonely n*****."

The star then cracks a joke about joining the Ku Klux Klan and is seen repeating the N-word numerous times in the 24-second clip, according to The Sun newspaper.

A source said, "Unfortunately this is the devastating reality of how Justin has behaved and reveals his attitude toward such a deeply emotive subject.

"People need to see this. Normal kids in society do not make these kind of jokes. He is protected by a network of staff, but the camera doesn't lie. This is the real Justin."

The new racism claim comes just days after Justin was forced to apologise for an earlier video in which he made an inappropriate joke about black people.

Justin said, "As a young man, I didn't understand the power of certain words and how they can hurt. I thought it was ok to repeat hurtful words and jokes, but didn't realise at the time that it wasn't funny and that in fact my actions were continuing the ignorance.

"Thanks to friends and family I learned from my mistakes and grew up and apologised for those wrongs. Now that these mistakes from the past have become public I need to apologise again to all those I have offended. I'm very sorry."